In the field of signal detection, the key problem which must be solved, is how to distinguish between noise alone, and the presence of one or more signals together with noise. This is a well known problem and many methods and devices are known for solving it. Conventional beamformers have been used to provide a more sensitive solution to the signal detection problem. However, they are typically used in the traditional manner of forming a directional beam and looking for signals in a particular direction. Spatial diversity methods which use multiple transducers have also been previously proposed. Neither of these techniques provides optimum energy detection sensitivity.